ix I Intermediate f'nreiifral Ann 227 



Another point, this time of a histological nature, which one has had in mind in 

 formulating the proposition under consideration, is the remarkable variation in number of the 

 Bete cells in different divisions of 1 he " procentral " area. As has been shown in a former 

 chapter, the total number of these elements in the arm area, speaking collectively, is 

 infinitely smaller than the same in the leg area. Of course this applies to man, in the 

 anthropoid ape the disparity is also marked but hardly so great, and the question at once 

 arises, whether there is any connection between this extraordinary fact and the assumption 

 of the erect posture ? To clear this point we shall have to see what the ratio is in pure 

 quadrupeds. But while the cortical cell lamination has been investigated in some of the 

 desired animals, for instance 1 , the sheep and cat, by Bevan Lewis 1 , neither has the motor 

 area in these animals been mapped out by approved methods, nor have the giant "motor" 

 cells been counted in serial sections, accordingly precise information on the point is wanting; 

 still it will be surprising if with the increased use of the anterior extremity in the automatic 

 movements involved in progression, there is no corresponding addition to the number of 

 giant cells in the forelimb area. 



In this view of the part played by the cells of Betz in the motor act certain 

 peculiarities in their histological constitution and the position they occupy must be taken 

 into account. Thus their position in point of lamination is most peculiar, and it is for 

 this reason that Bolton argues, and I think with justice, that we cannot class them in the 

 same category as ordinary pyramidal cells. In the solitary cells of Meynert peculiar to 

 the ' visuo-sensory " area Bolton sees homologous elements, and with this I also agree, but 

 into the class I would admit the large sub-stellate cells I have pointed out in the "audito- 

 sensory " and " postcentral " areas and perhaps deep-seated and special elements in the 

 pyriform lobe and cornu ammonis. According to this, homologous cells having remarkable 

 histological peculiarities occupy the depths of the cortex, not only in the motor area but 

 in all the primary centres controlling the functions by means of which the competition for life 

 is maintained ; these centres and probably kindred cells are necessarily represented, although 

 in varying degrees of perfection, throughout the vertebrate series, and it follows that the 

 cells peculiar to these centres must take first place in the procession of phylogenetic develop- 

 ment. Now in the lowest vertebrates it is probable that the crude automatic movements 

 of which they are alone capable are actuated by stimuli proceeding from a primitive cortical 

 collection of Betz cells, and taking a step lower, the chain of ganglia composing the 

 invertebrate nervous system may be likened to the combination of the Betz cells with 

 the "motor" cells in the pons, medulla, and cord, and I may here say that in man, the 

 ape, and lower animals many structural characters of the Betz cell are repeated in the anterior 

 cornual cell of the spinal cord. 



SUMMARY. 



1. The cortical field to which the name "intermediate precentral" is attached, ranges 

 as a zone between 3'5 and 1 cm. in width, placed after the manner of a buffer in front 

 of the "precentral" area proper and showing an additional extension downwards on to the 

 orbital surface of the hemisphere. Broadest, above, the area becomes constricted at its middle 

 and then expands again below. 



1 In Bevan Lewis's account of the examination of the Betz cells in the cortex cerebri of the cat and sheep it 

 is stated that compared with other parts the clusters are especially large and deuse in that portion of the sigmoid 

 gyms enveloping the lateral extremity of the cruciate sulcus, and this is the part supposed to control forelimb 

 movements. (Further observations in this direction will be offered in the Addendum.) 



292 



